The broad objective of this project is to understand the molecular basis of recombination in E. coli. Systems are being developed which will be stuitable for detection of recombination in vitro. In one system, two col E DNA derivatives, col E trp and col E kan, are used as substrates for the recombination process. Production of a fused col E trp kan would be detected as linked genes in a transformation assay. In another system, a transducing phage containing a duplication of the trp operon will be prepared. Two non-identical, non-complementing trp E alleles will be present. Internal recombination and reduction to haploidy for trp would be capable of generating trp E plus phage. Detection of recombination in this system would be possible even at low levels. Development of such assays for recombination in vitro would establish a system which would permit isolation and characterization of cellular components which are active in different steps of the recombination process. BIBLIOGRAPHIC REFERENCE: D. Zipkas and M. Riley, "A Simplified Method for Mapping by Conjugation", Journal of Bacteriology, April 1976 (in press).